This invention relates in general to communication with optical signals and, more particularly, to a method and apparatus for facilitating communication using optical signals which include multiple signal components that each have a respective different wavelength.
Telecommunications is a field which has been rapidly evolving over the past twenty years, fueled in part by the progressively increasing popularity of technologies such as cellular telephones, facsimile machines, and computer communications that use the Internet. Due to these growing new technologies, there has been a progressively increasing demand for telecommunications equipment with greater information-carrying capacity, which in turn has created a progressively increasing focus on effecting communications through the use of optical signals.
Through use of existing techniques such as dense wavelength division multiplexing (DWDM), a single optical fiber in a telecommunications system will frequently be carrying many component optical signals at respective different wavelengths, and each such component optical signal will be a time division multiplexed (TDM) signal that carries a number of separate telephone conversations or other ongoing communications. To the extent that optical signals are being used in this manner to transmit large amounts of information, techniques are needed for efficiently and cheaply processing optical signals, including demultiplexing of optical signals, multiplexing of optical signals, and switching of optical signals.
Many existing techniques for processing optical signals involve assemblies which are complex and which present difficult alignment problems that can produce relatively high optical losses. Other systems convert the optical data into electrical signals, subsequently carry out processing of the electrical signals to effect steps such as multiplexing, demultiplexing and switching, and then convert the electrical signals back into optical signals. The equipment used to effect these conversions introduces a significant delay into handling of the signals. All of these approaches are relatively expensive.
Some consideration has been given to fusing optical fibers in order to eliminate certain coupling or collimating optics, but the resulting devices are generally difficult to produce. Consideration has also been given to optical switches that use liquid crystals, bubbles, or micro-electro-opto-mechanical devices (MEMS), but these arrangements have relatively slow response times, on the order of a few milliseconds, and typically require a number of optical components that make them relatively complex and expensive, and that tend to result in relatively high optical losses.
From the foregoing, it may be appreciated that a need has arisen for a method and apparatus for processing optical signals, which avoid at least some of the problems discussed above. According to a first from of the present invention, a method and apparatus are provided to address this need, and involve first and second waveguides, and a coupling portion operable to cause radiation at a first wavelength which is traveling in a direction of travel through the first waveguide and which reaches the coupling portion to be routed so as to be traveling in one of the first and second waveguides when exiting the coupling portion, and to cause radiation at a second wavelength different from the first wavelength which is traveling through the first waveguide in the direction of travel and which reaches the coupling portion to be routed so as to be traveling in the other of the first and second waveguides when exiting the coupling portion. The coupling portion includes the first and second waveguides respectively having first and second portions that extend approximately parallel to each other and that are sufficiently close for a sufficient distance to permit coupling therebetween of radiation having at least one of the first and second wavelengths, and includes structure operable along at least part of the distance to frustrate coupling between the first and second portions of radiation having one of the first and second wavelengths while permitting coupling between the first and second portions of radiation having the other of the first and second wavelengths.
According to another form of the invention, a method involves: providing a first layer made of a material which has a first index of refraction; forming on the first layer first and second elongate sections made of a second material which is transmissive to radiation of a predetermined wavelength and which has a second index of refraction different from the first index of refraction; and forming over the elongate sections and exposed portions of the first layer a third layer made of a material which has a third index of refraction different from the second index of refraction, wherein the elongate sections function as cores of respective waveguides, and the materials of the first and second layers function as cladding for the cores.